Theoretical Investigations of Lead-Free Halide Perovskites Na₂AgInY₆ (Y = Cl, Br, I) for Transport and Optoelectronic Devices

Lead-free double perovskites are stable, non-toxic, and have high conversion efficiency, better oxidation resistance, and high-temperature stability, making them promising for optoelectronic and thermoelectric materials. In the current report, we have examined structural, electronic, optical, and transport characteristics of Na2AgInY6 (Y = Cl, Br, I) utilizing DFT-based Wien2k code. Thermodynamic stability is verified by calculating the enthalpy of formation. TB-mBJ measures the bandgap computations, and the investigated compositions have indirect bandgaps. The bandgap values are decreased from 3.1 eV to 1.2 eV as the halide ion is replaced from Cl - I. This substitution-dependent tuning of band edge across the visible-infrared boundary makes them favorable for solar cell applications. The optical response is evaluated by measuring the refractive index, dielectric constant, absorption coefficient, and reflectivity. The thermoelectric efficiency of Na2AgInY6 (Y = Cl, Br, I) is calculated by figure of merit and power factor. The findings of this study unveil the potential of these novel compositions for next-generation energy harvesting devices, including solar cells and thermoelectric devices. (c) 2023 The Electrochemical Society ("ECS").